The present invention relates to a flat gasket as it is in particular used in vehicles. Such flat gaskets are for instance applied as gaskets in the exhaust line of combustion engines, as cylinder head gaskets or also as control plates for hydraulic systems. Control plates for hydraulic systems, such as transmission control plates in addition to the fluid control function simultaneously have a sealing function.
Flat gaskets often show a multi-layered construction. The first layer that is used is usually a distance layer, which due to its predetermined thickness establishes a particular distance between the two parts interconnected through the flat gasket. As a further layer, a first gasket layer can be found on top of this first distance layer, which may for instance comprise sealing elements such as beads or coatings. Such gasket layers provide for the actual sealing between the parts interconnected through the flat gasket and in the following are referred to as sealing layers. Further layers may be added.
With such multi-layered flat gaskets, it is required that the individual layers are connected to each other at least for their transport until the final installation, so that a flat gasket can be handled as a unit. To this end, the layers are conventionally welded or riveted to each other or connected with one another by folding over of the edges of the layers.
These conventional connection techniques show a plurality of disadvantages. Practice has shown that a layer interconnection via welding points always also causes welding sputter, which gets loose after the installation of the flat gasket and which may lead to a blocking of passage openings in the flat gasket or in the adjacent parts. Moreover, welding methods can only be applied for gasket layers which are not coated.
Interconnection of two gasket layers using a rivet in the area of the rivet causes a thickening or a local protrusion of the rivet over the gasket layers. Further, riveting always causes formation of chips, these chips can be carried on to the passage openings of the flat gasket or also of an adjacent part. Finally, a rivet connection requires the use of additional parts, namely the rivets, and additional connection steps.
Folding over of the edges for the interconnection of neighboring gasket layers requires a purposeful design of the outer edge of the neighboring layers, either by steps, by an inclined course, by deliberate recesses or the like. This increases the effort for the production of the tooling. In addition, the gasket layers this way can only be connected to each other at their outer edges. Folding over, too, causes a thickening of the flat gasket in the area with the folded-over edge.
This is also the case if the layers are connected to each other by clinching. This also applies for the related method of tox clinching.